An internal combustion engine includes a plurality of cylinders. Each cylinder has a combustion chamber in which the combustion process takes place. The combustion is initiated in each of the cylinders in a sequenced manner. If in one or more of the engine cylinders the combustion process does not take place as it should be, the engine is said to have misfired. There are several causes of engine misfiring. Some of the most common ones include spark plugs or spark plug wires defects, or mechanical defects of the cylinders or the valves.
The combustion creates great pressure changes within the cylinder and resultant great torques on the engine. These torques cause the engine to vibrate and in some cases to displace. When the engine is misfiring, an abnormal engine displacement is created. This abnormal displacement can cause uncomfortable shaking of the vehicle or premature wear of components of the engine.
Traditional methods to detect if one or more cylinder has misfired include using a plurality of sensors which monitor the combustion in each of the cylinders. These sensors include one or more of exhaust gas sensors, pressure sensors, ion-current sensors. While information about which one of the cylinders is defective can be readily obtained, the rough environment the sensors operate in disfavours using such complex sensing system applied to each cylinder. In addition, the sensors are usually expensive and frequent replacement can hinder the practical application of such method. Other methods which exclude direct measurements use mathematical modeling. While the models answer some of the inconveniences of the direct measurements methods, the models include several assumptions which may render the output of the method inaccurate or imprecise. Furthermore, the models may require long processing time that may not allow real-time analysis.
Therefore, there is a need for a method of detecting misfiring in one or more of the cylinders of an internal combustion engine which can easily be implemented and is reliable.